From the 1st January the Transport and Security Administration (TSA) will enforce new regulations governing the carrying of lithium batteries on aircraft.
The regulations prohibit the carrying of any ‘spare' or ‘loose' lithium batteries in checked baggage. This is obviously due to the violent explosions that result in physical damage to a lithium cell -- their delicate nature combined with the commonplace manhandling of luggage in most airports around the world could pose a serious risk! This video from YouTube shows just what happens when a lithium battery pack is punctured... serious stuff! I'm pretty sure this is the type if incident that the TSA are trying to avoid with these new regulations as passengers are still allowed to pack lithium items in their checked luggage so long as the battery is installed in a device. I guess the cell-phone, PDA or other consumer electronic item is deemed to give the cell enough protection from knocks and bumps to reduce the risk of fire to an acceptable level. This theory is reinforced by the fact that loose lithium batteries can be carried in carry-on luggage, assuming of course that you follow the tips and guidelines while packing.
There are overall limits on the amount of lithium power you can carry on a flight, which includes both spare and installed batteries. The quotas are expressed in grams of lithium content. For a full explanation take a look at the official SafeTravel.dot.gov website.
While it's good to see a restriction on the carrying of loose lithium cells and battery packs on board aircraft, I still find myself a little concerned over lithium power allowed. The major causes of the spontaneous combustion of lithium cells seem to be: physical damage, internal-short circuits (in the cells or devices they power), and overcharging. While these new regulations are trying to tackle the first cause I wonder what's being done about the others. Internal short-circuits are the cause of many consumer electronic devices bursting in to flames, overcharging is a sure fire way to make that notebook burn a hole in your lap and a real danger with most airlines offering laptop power outlets at your seat.
Of course the chances of these things happening are low and only a tiny fraction of devices end up malfunctioning, but as the number of small electronic devices we carry around increases, it's only a matter of time until a serious incident forces the authorities to take a firmer line. Desiree Everts over at CNET's News.com pointed out that lithium batteries could not be ruled out as a potential cause of the on board fire at Philadelphia National Airport last year.